Hellfire is a single-player expansion pack to Diablo developed by Synergistic Software, a Sierra division. Hellfire's storyline occurs as an aside to the main story arc of the original game. A sorcerer, while performing a ritual, unknowingly releases the demon Na-Krul unto the town of Tristram, but before it can completely escape, the sorcerer magically seals the doors. The player is later tasked with venturing into Na-Krul's lair and vanquishing it...